I am the bearer of both good and bad news I am afraid.
The good ___ Alphagraphix card kit people do (or did) a 7mm scale card kit of two of the coaches together with a loco. I know that they did because I bought one such kit many years ago. It was one of their smaller kits and didn't cost very much even out here
The bad ____ It is safely stored in the 'card kits' folder and I absolutely NO idea where that is
(not where I expected it to be when I went looking)
If I do manage to find it in the next day or so I will send you the basic dimensions but please don't hold your breath.
Sorry I couldn't be more helpful